SMITH COUNTY. 209 



they are thin, discontinuous, and of a physically different ore than the main 

 bed. This would tend to show that the ore bed found on the benches be- 

 longed at the level of and had once been part of the main bed. 



"2. The greensand underlying the ore bed varies from thirty to forty 

 feet thick, yet when there are several benches on the hill slope, and we 

 measure the vertical thickness of th>- greensand from the upper ore bed to 

 the base of the outcrop, it often appears almost a hundred feet thick. This 

 can only be explained by supposing the edge of the hill to have slipped. 



"The alternation of hard a'nd soft strata doubtless causes the formation of 

 many benches, but this generally occurs in the country north of the Sabine, 

 where almost all the benches are due to it. The soft strata over a harder 

 one are worn away, until the eroding agencies come to the hard floor, which 

 temporarily arrests the denudation, and hence arises a bench. The number 

 of bencnes that can be explained as sea beaches, or river and lake terraces, 

 is exceedingly doubtful, and the want of contour maps, as well as the con- 

 cealed condition of all the strata, makes it still more difficult to determine 

 the extent to which this cause has operated. No satisfactory work can be 

 done in the matter until good maps are obtainable." 



Eight miles southeast of Tyler this structure is well represented. Here the 

 benches are two in number. A section gives: 



1 . Soil and sand 1 to 1 feet 



2. Angular sandstone i to 1 inch. 



3. Black laminated ore . 6 to 10 inches. 



4. Altered greensand 10 feet. 



5. Red sand clay, at base exposed 50 feet. 



One mile west of Steen Saline and four miles east of Lindale, the same 

 structure may be seen again. At this locality I counted no less than four 

 benches, which are probably due to landslides. Good ore of the black lami- 

 nated variety was seen in all four benches. In many other places in the 

 county their structure is well illustrated. 



DESCRIPTION OF THE IRON ORES. 



The iron ores of Smith County may be classed as brown hematites, other- 

 wise known as limonites. They have as a rule from five to twenty per cent 

 of water, three to thirty-five per cent of silica, from two to twenty per cent 

 of alumina, with small amounts of lime and magnesia. The metallic iron 

 varies from twenty to fifty-six per cent. These ores are high in phosphoric 

 acid, some of them having as high as one per cent, and the average being 

 about four-tenths of one per cent. The sulphur is not so high, as many of the 

 ores have only a trace of it. 



